You may have encountered an error message that says Cisco debug nat. There are several steps you can take to fix this problem, so we’ll take a look at that now.
Use the no ip nat inside command to prevent the location from being moved in future transfers.Use the clear ip nat translation command if you want to clear IP-NAT translations.Change your NAT configuration.
When there are problems with IP connectivity in a NAT environment, it is often very difficult to determine the cause of the failure. It is often mistakenly accused of NAT, but in reality there is a fundamental problem. This document shows how to use tools to validate NAT operations on available Cisco concentrators. This document also shows how to helpHelp you troubleshoot basic NAT problems and how to avoid common NAT troubleshooting mistakes.
This document is not limited to specific software and hardware versions.
The information in this document was generated by devices in the selected lab environment. All devices used in this document were started with rid configuration (default). As you build your network, make sure you understand the long-term implications of each order.
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When trying to determine the IP factor of a connection problem, NAT exclusion will help. Follow these precautions to ensure NAT is working as expected:
Use the entire configuration to clearly define what NAT should achieve. At this point, you can see that when usingThere was a problem using the configuration. For help setting up NAT, see Configuring Network Address Translation: Getting Started.
Check if there are translations in the translation table.
Use the show and debug codes to ensure that the translation is in progress.
How do you troubleshoot NAT?
Check in detail what is going on with the packet and make sure the new routers have the correct routing information to forward the packet.
Below are a few problems in which we will use the steps above to identify the source of all problems.
In this network diagram, Router 4 can ping Router 5 (172.16.6.5) but not Router 6 (172.16.11.7):
There is no history log for any of the modems, and Router 4 has Router 6 as the default gateway. Router 6 is configured with NAT as follows:
Router 6
Ethernet0 interface Internet address 172.16.6.6 255.255.255.0 broadcast IP address Nat IP address outside 10BaseT Support type!Ethernet interface1 IP Coverage 10.10.10.6 255.255.255.0 ip to nat Media Type 10BaseT !2.7 point-to-point serial interface IP concentration at 172.16.11.6 255.255.255.0 Frame Relay ip nat outside Dlci interface instructions !ip nat pool test 172.16.11.70 172.16.11. prefix length seventy-one 24thip nat some pool tests in source listip nat in original sentence 10.10.10.4 172.16.6.14 !Allow Access List 7 10.10.50.4Access list 7 licenses 10.10.60.4Allow Access List 7 10.10.70.4
First, make sure NAT is working properly. From the configuration, you know that the IP address of Router 4 (10.10.10.4) should be statically translated to 172.16.6.14. You can of course use the show ip nat translation statement on Router 6 to check if there is a translation in the blackjack translation table:
router-6 # show translation ip natPro Inside Global Inside Local Outside Local Outside Global--- 172.16.6.14 10.10.10.4 --- ---
Use the configuration to determine exactly what NAT should receive.Make sure the translation table contains the correct translations.Use the display and debug instructions to ensure that the translation works.
Now check that this conversion can happenwhen the original IP traffic is from Router 4. This can be done on 6+ paired routers by running NAT debugging or by monitoring NAT statistics with the show ip nat statistics command. Because debug commands should only be used as a last resort, with the verify command.
The goal is to track the hit set to see if the way traffic from Router 4 is being sent increases. The hit counter is incremented each time a translation from the translation table is used to help you translate the address. Clear the numbers first, then view the statistics, try to ping Router 4 to Router 7, then view the statistics again.
Router-6 # suppresses IP-Nat statisticsRouter-6 #router-6 # ip nat usually displaysTotal number of active broadcasts: 1 (1 static, zero dynamic; 0 extended)External interfaces:Ethernet0, serial 2.7 Internal interfaces: Ethernet1 Moves: 0 Rejections: 0 Overdue transfers: 0 Dynamic missions: - Internal source access list 7 test billiards refcount 0 Teststh group: netmask 255.255.255.0 stop 172.16.11.70 end 172.16.11.71 General type, only a few addresses, assigned 0 misses (0%), 0Router-6 #
After using ping 172.16.11.7 on Router 4, the NAT statistics on a 50% router looks like this:
to prove
Open the router’s configuration web page.You will then be asked the truth about your connection.Click the Status tab.Scroll down and find the config type panel and see if you have a private or public IP address.
router-6 # displays nat statistics for an IP address Total number of active transfers: 1 (1 tone, 0 dynamic; 0 extended) External interfaces: Ethernet0, serial 2.7 Internal interfaces: Ethernet1 Views: Chess Offers: 0 Overdue transfers: 0 Dynamic missions: - Internal source Access List 7 Check Pool 0 Pool test refcount: netmask 255.255.255.0 Focus on 172.16.11.70 end 172.16.11.71 Generic type, contains 2 in total, 0 faults assigned (0%), 0
You can tell from the show teams that vacations increase the number of visits. For a successful ping from the router, Cisco must increase the number of hits by ten. The five Internet Control Message Protocol (ICMP) echo messages sent by the receiving router (routing)Cat 4) must be translated, and the five echo reply packets from the largest target router (Router 7) must also be translated a little more strictly. just ten strokes. The five missing results are most likely due to the echo replies not providing translation or being sent by Router 7.
Make sure Router 7 will definitely not send echo reply packets to Router 4. First, check what NAT is for the packet. Router 4 processes ICMP echo packets with a source address of 10.10.10. And 4 destination addresses, which is associated with 172.16.11.7. After NAT, packet 7 received by the router has a received address of 172.16.6.1, and packet 4 has a sort of destination of 172.16.11.7. Router 7 must respond to 172.16.6.14, and since 172.16.6.14 is not very directly connected to Router 7, it needs a route for that network in the draft to respond. Check the routing craps table of Router 7 to see if the route exists.
router-7 # shows the IP routeCodes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP. D - EIGRP,EX - external EIGRP, O - OSPF, IA - OSPF dis zone - n1 OSPF External NSSA type 1, N2 - OSPF External NSSA type 2 E1 - External OSPF type 1, E2 - External OSPF type 2, E - EGP post - IS-IS, L1 - IS-IS Level-1, L2 - IS-IS Level-2, ia - IS-IS dis zone 6. - standard candidate, U - single route per user, o - ODR P - static route saved periodicallyGateway of last resort is completely undefined 172.16.0.0/24 can be described as subnet, 4 subnetsC 172.16.12.0 connected directly, Serial0.8C 172 .16.9.0 can be connected directly, Serial0.5C 172.16.11.0 is also straight, Serial0.6C 172.16.5.0 directly connected, Ethernet0
How do I know if my NAT is working?
You can see that the routing counter for Router 7 is not
